The Krüppel-like zinc finger protein Glis2 functions as a negative modulator of the Wnt/beta-catenin signaling pathway

Nephronophthisis: a pathological and genetic perspective

Nephronophthisis (NPHP) is an autosomal recessive cystic kidney disease and is one of the most frequent genetic causes for kidney failure (KF) in children and adolescents. Over 20 genes cause NPHP and over 90 genes contribute to renal ciliopathies often involving multiple organs. About 15-20% of NPHP patients have additional extrarenal symptoms affecting other organs than the kidneys. The involvement of additional organ systems in syndromic forms of NPHP is explained by shared expression of most NPHP gene products in centrosomes and primary cilia, a sensory organelle present in most mammalian cells. This finding resulted in the classification of NPHP as a ciliopathy. If extrarenal symptoms are present in addition to NPHP, these disorders are defined as NPHP-related ciliopathies (NPHP-RC) and can involve the retina (e.g., with Senior-Løken syndrome), CNS (central nervous system) (e.g., with Joubert syndrome), liver (e.g., Boichis and Arima syndromes), or bone (e.g., Mainzer-Saldino and Sensenbrenner syndromes). This review focuses on the pathological findings and the recent genetic advances in NPHP and NPHP-RC. Different mechanisms and signaling pathways are involved in NPHP ranging from planar cell polarity, sonic hedgehog signaling (Shh), DNA damage response pathway, Hippo, mTOR, and cAMP signaling. A number of therapeutic interventions appear to be promising, ranging from vasopressin receptor 2 antagonists such as tolvaptan, cyclin-dependent kinase inhibitors such as roscovitine, Hh agonists such as purmorphamine, and mTOR inhibitors such as rapamycin.

GLIS2 and CCND1 expression levels in breast cancer patients

BACKGROUND

Breast cancer (BC) is the most prevalent cancer in women, with increasing incidence and death rates in recent years. Disruptions of different signaling pathways partially cause breast cancer. Hence, different genes through particular pathways are involved in BC tumorigenesis.

METHODS

In this study, we evaluated the expression level of GLIS2 and CCND1 genes in 50 patients. Also, in-silico analyses were used to enrich related signaling pathways involving the mentioned genes.

RESULTS

The results showed an increased expression level of Cyclin D1 and decreased expression level of GLIS2 in BC patients. Moreover, a relationship between aberrant expression levels of GLIS2 and CCND1 and BC development was determined.

CONCLUSION

These observations could help uncover new therapeutic targets for treating patients with BC in the progressive stage.

circTAB2 inhibits lung cancer proliferation, migration and invasion by sponging miR-3142 to upregulate GLIS2

Circular RNAs (circRNAs) are a specialized circular structure, are deregulated in cancers and play essential roles in biological processes involved in tumor progression. However, the mechanism by which circRNAs affect lung tumorigenesis and progression remains largely unexplored. To investigate the role of circRNA in lung cancer, circRNA expression profile was screened by bioinformatics analysis. The levels of circTAB2, miR-3142, and GLIS family zinc finger 2 (GLIS2) were measured by quantitate real-time (qRT-PCR) or western blot. Cell proliferation, apoptosis, migration and invasion were detected by EdU, flow cytometry, and transwell assays, respectively. Bioinformatics, western blot, RIP, pull down, dual luciferase reporter and rescue experiments were used to verify the direct relationship between miR-3142 and circTAB2 or GLIS2. The xenograft assays were used to assess the role of circTAB2 in vivo.CircTAB2 exhibited low expression in cancer tissues. Gain and loss-of-function assays indicated that circTAB2 could inhibit cell proliferation, migration and invasion. Functional studies revealed that circTAB2 acted as a miRNA sponge, directly interacted with miR-3142 and consequently regulated GLIS2 /AKT. Taken together, circTAB2 serves as an inhibitory role in lung cancer through a novel circTAB2 /miR-3142 /GLIS2 /AKT pathway and could be exploited a novel marker in lung cancer.

GLIS1-3: Links to Primary Cilium, Reprogramming, Stem Cell Renewal, and Disease

The GLI-Similar 1-3 (GLIS1-3) genes, in addition to encoding GLIS1-3 Krüppel-like zinc finger transcription factors, also generate circular GLIS (circGLIS) RNAs. GLIS1-3 regulate gene transcription by binding to GLIS binding sites in target genes, whereas circGLIS RNAs largely act as miRNA sponges. GLIS1-3 play a critical role in the regulation of many biological processes and have been implicated in various pathologies. GLIS protein activities appear to be regulated by primary cilium-dependent and -independent signaling pathways that via post-translational modifications may cause changes in the subcellular localization, proteolytic processing, and protein interactions. These modifications can affect the transcriptional activity of GLIS proteins and, consequently, the biological functions they regulate as well as their roles in disease. Recent studies have implicated GLIS1-3 proteins and circGLIS RNAs in the regulation of stemness, self-renewal, epithelial-mesenchymal transition (EMT), cell reprogramming, lineage determination, and differentiation. These biological processes are interconnected and play a critical role in embryonic development, tissue homeostasis, and cell plasticity. Dysregulation of these processes are part of many pathologies. This review provides an update on our current knowledge of the roles GLIS proteins and circGLIS RNAs in the control of these biological processes in relation to their regulation of normal physiological functions and disease.

Prioritization of Genes Relevant to Bone Fragility Through the Unbiased Integration of Aging Mouse Bone Transcriptomics and Human GWAS Analyses

Identifying new genetic determinants of bone mineral density (BMD) and fracture promises to yield improved diagnostics and therapies for bone fragility. However, prioritizing candidate genes from genome-wide screens can be challenging. To overcome this challenge, we prioritized mouse genes that are differentially expressed in aging mouse bone based on whether their human homolog is associated with human BMD and/or fracture. Unbiased RNA-seq analysis of young and old male C57BL/6 mouse cortical bone identified 1499, 1685, and 5525 differentially expressed genes (DEGs) in 1, 2, and 2.5-year-old bone, relative to 2-month-old bone, respectively. Gene-based scores for heel ultrasound bone mineral density (eBMD) and fracture were estimated using published genome-wide association studies (GWAS) results of these traits in the UK Biobank. Enrichment analysis showed that mouse bone DEG sets for all three age groups, relative to young bone, are significantly enriched for eBMD, but only the oldest two DEG sets are enriched for fracture. Using gene-based scores, this approach prioritizes among thousands of DEGs by a factor of 5- to 100-fold, yielding 10 and 21 genes significantly associated with fracture in the two oldest groups of mouse DEGs. Though these genes were not the most differentially expressed, they included Sost, Lrp5, and others with well-established functions in bone. Several others have, as yet, unknown roles in the skeleton. Therefore, this study accelerates identification of new genetic determinants of bone fragility by prioritizing a clinically relevant and experimentally tractable number of candidate genes for functional analysis. Finally, we provide a website (www.mouse2human.org) to enable other researchers to easily apply our strategy. © 2022 American Society for Bone and Mineral Research (ASBMR).

An EMT-primary cilium-GLIS2 signaling axis regulates mammogenesis and claudin-low breast tumorigenesis

The epithelial-mesenchymal transition (EMT) and primary ciliogenesis induce stem cell properties in basal mammary stem cells (MaSCs) to promote mammogenesis, but the underlying mechanisms remain incompletely understood. Here, we show that EMT transcription factors promote ciliogenesis upon entry into intermediate EMT states by activating ciliogenesis inducers, including FGFR1. The resulting primary cilia promote ubiquitination and inactivation of a transcriptional repressor, GLIS2, which localizes to the ciliary base. We show that GLIS2 inactivation promotes MaSC stemness, and GLIS2 is required for normal mammary gland development. Moreover, GLIS2 inactivation is required to induce the proliferative and tumorigenic capacities of the mammary tumor–initiating cells (MaTICs) of claudin-low breast cancers. Claudin-low breast tumors can be segregated from other breast tumor subtypes based on a GLIS2-dependent gene expression signature. Collectively, our findings establish molecular mechanisms by which EMT programs induce ciliogenesis to control MaSC and MaTIC stemness, mammary gland development, and claudin-low breast cancer formation.

Hedgehog Signaling: Implications in Cancers and Viral Infections

The hedgehog (SHH) signaling pathway is primarily involved in embryonic gut development, smooth muscle differentiation, cell proliferation, adult tissue homeostasis, tissue repair following injury, and tissue polarity during the development of vertebrate and invertebrate organisms. GLIoma-associated oncogene homolog (GLI) family of zinc-finger transcription factors and smoothened (SMO) are the signal transducers of the SHH pathway. Both SHH ligand-dependent and independent mechanisms activate GLI proteins. Various transcriptional mechanisms, posttranslational modifications (phosphorylation, ubiquitination, proteolytic processing, SUMOylation, and acetylation), and nuclear-cytoplasmic shuttling control the activity of SHH signaling pathway proteins. The dysregulated SHH pathway is associated with bone and soft tissue sarcomas, GLIomas, medulloblastomas, leukemias, and tumors of breast, lung, skin, prostate, brain, gastric, and pancreas. While extensively studied in development and sarcomas, GLI family proteins play an essential role in many host-pathogen interactions, including bacterial and viral infections and their associated cancers. Viruses hijack host GLI family transcription factors and their downstream signaling cascades to enhance the viral gene transcription required for replication and pathogenesis. In this review, we discuss a distinct role(s) of GLI proteins in the process of tumorigenesis and host-pathogen interactions in the context of viral infection-associated malignancies and cancers due to other causes. Here, we emphasize the potential of the Hedgehog (HH) pathway targeting as a potential anti-cancer therapeutic approach, which in the future could also be tested in infection-associated fatalities.

Comprehensive Transcriptome Profiling of Cryptic CBFA2T3-GLIS2 Fusion-Positive AML Defines Novel Therapeutic Options: A COG and TARGET Pediatric AML Study

PURPOSE

A cryptic inv(16)(p13.3q24.3) encoding the CBFA2T3-GLIS2 fusion is associated with poor outcome in infants with acute megakaryocytic leukemia. We aimed to broaden our understanding of the pathogenesis of this fusion through transcriptome profiling.

EXPERIMENTAL DESIGN

Available RNA from children and young adults with de novo acute myeloid leukemia (AML; N = 1,049) underwent transcriptome sequencing (mRNA and miRNA). Transcriptome profiles for those with the CBFA2T3-GLIS2 fusion (N = 24) and without (N = 1,025) were contrasted to define fusion-specific miRNAs, genes, and pathways. Clinical annotations defined distinct fusion-associated disease characteristics and outcomes.

RESULTS

The CBFA2T3-GLIS2 fusion was restricted to infants <3 years old (P < 0.001), and the presence of this fusion was highly associated with adverse outcome (P < 0.001) across all morphologic classifications. Further, there was a striking paucity of recurrent cooperating mutations, and transduction of cord blood stem cells with this fusion was sufficient for malignant transformation. CBFA2T3-GLIS2 positive cases displayed marked upregulation of genes with cell membrane/extracellular matrix localization potential, including NCAM1 and GABRE. Additionally, miRNA profiling revealed significant overexpression of mature miR-224 and miR-452, which are intronic miRNAs transcribed from the GABRE locus. Gene-set enrichment identified dysregulated Hippo, TGFβ, and hedgehog signaling, as well as NCAM1 (CD56) interaction pathways. Therapeutic targeting of fusion-positive leukemic cells with CD56-directed antibody-drug conjugate caused significant cytotoxicity in leukemic blasts.

CONCLUSIONS

The CBFA2T3-GLIS2 fusion defines a highly refractory entity limited to infants that appears to be sufficient for malignant transformation. Transcriptome profiling elucidated several highly targetable genes and pathways, including the identification of CD56, providing a highly plausible target for therapeutic intervention.

Gene-Related Response of Basal Cell Carcinoma to Biologic Treatment with Vismodegib

We aimed to characterise the response of locally advanced basal cell carcinoma (BCC) to systemic treatment with Vismodegib, a Hedgehog pathway inhibitor, by changes in the expression levels of Hedgehog pathway genes. Data were collected prospectively on 12 patients treated systemically for locally advanced BCC. Biopsy samples taken on admission and after treatment cessation were analysed pathologically and with the NanoString nCounter system to quantify the expression of 40 Hedgehog signaling pathway genes. Findings were compared before and after treatment, between complete and partial responders, and with localised BCC samples from 22 patients. Sixteen Hedgehog pathway genes changed significantly from before to after treatment. GAS1 was the only gene with a significantly different expression at baseline between complete responders (6 patients) and partial responders (4 patients) to Vismodegib (P = 0.014). GAS, GLIS2 and PRKACG1 showed different expression before treatment between the locally advanced and localised BCCs. The baseline expression level of GAS1 appears to be predictive of the response of locally advanced BCC to systemic Vismodegib treatment. A change in expression of many Hedgehog pathway genes, albeit expected by the known activity of Vismodegib, may nevertheless serve as an indicator of the response potential of the tumour.

Emerging Roles of GLI-Similar Krüppel-like Zinc Finger Transcription Factors in Leukemia and Other Cancers

GLI-similar 1-3 (GLIS1-3), a subfamily of Krüppel-like zinc finger transcription factors, function as key regulators of several biological processes important to oncogenesis, including control of cell proliferation, differentiation, self-renewal, and epithelial-mesenchymal transition. This review provides a short overview of the critical roles genetic changes in GLIS1-3 play in the development of several malignancies. This includes intrachromosomal translocations involving GLIS2 and ETO2/CBFA2T3 in the development of pediatric non-Down's syndrome (DS), acute megakaryoblastic leukemia (AMKL), a malignancy with poor prognosis, and an association of interchromosomal translocations between GLIS3, GLIS1, and PAX8, and between GLIS3 and CLPTM1L with hyalinizing trabecular tumors (HTTs) and fibrolamellar hepatocellular carcinoma (FHCC), respectively. Targeting upstream signaling pathways that regulate GLIS signaling may offer new therapeutic strategies in the management of cancer.

Increased FLYWCH1 Expression is Negatively Correlated with Wnt/β-catenin Target Gene Expression in Acute Myeloid Leukemia Cells

Acute myeloid leukaemia (AML) is a heterogeneous clonal malignancy of hematopoietic progenitor cells. The Wnt pathway and its downstream targets are tightly regulated by β-catenin. We recently discovered a new protein, FLYWCH1, which can directly bind nuclear β-catenin. Herein, we studied the FLYWCH1/β-catenin pathway in AML cells using qRT-PCR, Western blot, and immunofluorescence assays. In addition, the stemness activity and cell cycle were analysed by the colony-forming unit (CFU) using methylcellulose-based and Propidium iodide/flow cytometry assays. We found that FLYWCH1 mRNA and protein were differentially expressed in the AML cell lines. C-Myc, cyclin D1, and c-Jun expression decreased in the presence of higher FLYWCH1 expression, and vice versa. There appeared to be the loss of FLYWCH1 expression in dividing cells. The sub-G0 phase was prolonged and shortened in the low and high FLYWCH1 expression cell lines, respectively. The G0/G1 arrest correlated with FLYWCH1-expression, and these cell lines also formed colonies, whereas the low FLYWCH1 expression cell lines could not. Thus, FLYWCH1 functions as a negative regulator of the Wnt/β-catenin pathway in AML.

The changing scenario of non-Down syndrome acute megakaryoblastic leukemia in children

Pediatric non-Down-syndrome acute megakaryoblastic leukemia (non-DS-AMKL) is a heterogeneous subtype of leukemia that has historically been associated with poor prognosis. Until the advent of large-scale genomic sequencing, the management of patients with non-DS-AMKL was very difficult due to the absence of reliable biological prognostic markers. The sequencing of large cohort of pediatric non-DS-AMKL samples led to the discovery of novel genetic aberrations, including high-frequency fusions, such as CBFA2T3-GLIS2 and NUP98-KDM5 A, as well as less frequent aberrations, such as HOX rearrangements. These new insights into the genetic landscape of pediatric non-DS-AMKL has allowed refining the risk-group stratification, leading to important changes in the prognostic scenario of these patients. This review summarizes the most important molecular pathogenic mechanisms of pediatric non-DS-AMKL. A critical discussion on how novel genetic abnormalities have refined the risk profile assessment and changed the management of these patients in clinical practice is also provided.

Functional Analysis of Promoter Variants in Genes Involved in Sex Steroid Action, DNA Repair and Cell Cycle Control

Genetic variants affecting the regulation of gene expression are among the main causes of human diversity. The potential importance of regulatory polymorphisms is underscored by results from Genome Wide Association Studies, which have already implicated such polymorphisms in the susceptibility to complex diseases such as breast cancer. In this study, we re-sequenced the promoter regions of 24 genes involved in pathways related to breast cancer including sex steroid action, DNA repair, and cell cycle control in 60 unrelated Caucasian individuals. We constructed haplotypes and assessed the functional impact of promoter variants using gene reporter assays and electrophoretic mobility shift assays. We identified putative functional variants within the promoter regions of estrogen receptor 1 (ESR1), ESR2, forkhead box A1 (FOXA1), ubiquitin interaction motif containing 1 (UIMC1) and cell division cycle 7 (CDC7). The functional polymorphism on CDC7, rs13447455, influences CDC7 transcriptional activity in an allele-specific manner and alters DNA–protein complex formation in breast cancer cell lines. Moreover, results from the Breast Cancer Association Consortium show a marginal association between rs13447455 and breast cancer risk (p = 9.3 × 10⁻⁵), thus warranting further investigation. Furthermore, our study has helped provide methodological solutions to some technical difficulties that were encountered with gene reporter assays, particularly regarding inter-clone variability and statistical consistency.

CBFA2T3-GLIS2-positive acute myeloid leukaemia. A peculiar paediatric entity

The scenario of paediatric acute myeloid leukaemia (AML), particularly non‐Down syndrome acute megakaryoblastic leukaemia (non‐DS‐AMKL), has been recently revolutionized by the advent of large‐scale, genomic sequencing technologies. In this changing landscape, a significantly relevant discovery has been represented by the identification of the CBFA2T3‐GLIS2 fusion gene, which is the result of a cryptic inversion of chromosome 16. It is the most frequent chimeric oncogene identified to date in non‐DS‐AMKL, although it seems not to be exclusively restricted to the French‐American‐British M7 subgroup. The CBFA2T3‐GLIS2 fusion gene characterizes a subtype of leukaemia that is specific to paediatrics, having never been identified in adults. It characterizes an extremely aggressive leukaemia, as the presence of this fusion is associated with a grim outcome in almost all of the case series reported, with overall survival rates ranging between 15% and 30%. Although the molecular basis that underlies this leukaemia subtype is still far from being completely elucidated, unique functional properties induced by CBFA2T3‐GLIS2 in the leukaemogenesis driving process have been recently identified. We here review the peculiarities of CBFA2T3‐GLIS2‐positive AML, describing its intriguing clinical and biological behaviour and providing some challenging targeting opportunities.

GLIS1-3 transcription factors: critical roles in the regulation of multiple physiological processes and diseases

Krüppel-like zinc finger proteins form one of the largest families of transcription factors. They function as key regulators of embryonic development and a wide range of other physiological processes, and are implicated in a variety of pathologies. GLI-similar 1-3 (GLIS1-3) constitute a subfamily of Krüppel-like zinc finger proteins that act either as activators or repressors of gene transcription. GLIS3 plays a critical role in the regulation of multiple biological processes and is a key regulator of pancreatic β cell generation and maturation, insulin gene expression, thyroid hormone biosynthesis, spermatogenesis, and the maintenance of normal kidney functions. Loss of GLIS3 function in humans and mice leads to the development of several pathologies, including neonatal diabetes and congenital hypothyroidism, polycystic kidney disease, and infertility. Single nucleotide polymorphisms in GLIS3 genes have been associated with increased risk of several diseases, including type 1 and type 2 diabetes, glaucoma, and neurological disorders. GLIS2 plays a critical role in the kidney and GLIS2 dysfunction leads to nephronophthisis, an end-stage, cystic renal disease. In addition, GLIS1-3 have regulatory functions in several stem/progenitor cell populations. GLIS1 and GLIS3 greatly enhance reprogramming efficiency of somatic cells into induced embryonic stem cells, while GLIS2 inhibits reprogramming. Recent studies have obtained substantial mechanistic insights into several physiological processes regulated by GLIS2 and GLIS3, while a little is still known about the physiological functions of GLIS1. The localization of some GLIS proteins to the primary cilium suggests that their activity may be regulated by a downstream primary cilium-associated signaling pathway. Insights into the upstream GLIS signaling pathway may provide opportunities for the development of new therapeutic strategies for diabetes, hypothyroidism, and other diseases.

Emergence of TNIK inhibitors in cancer therapeutics

The outcome of patients with metastatic colorectal cancer remains unsatisfactory. To improve patient prognosis, it will be necessary to identify new drug targets based on molecules that are essential for colorectal carcinogenesis, and to develop therapeutics that target such molecules. The great majority of colorectal cancers (>90%) have mutations in at least one Wnt signaling pathway gene. Aberrant activation of Wnt signaling is a major force driving colorectal carcinogenesis. Several therapeutics targeting Wnt pathway molecules, including porcupine, frizzled receptors and tankyrases, have been developed, but none of them have yet been incorporated into clinical practice. Wnt signaling is most frequently activated by loss of function of the adenomatous polyposis coli (APC) tumor suppressor gene. Restoration of APC gene function does not seem to be a realistic therapeutic approach, and, therefore, only Wnt signaling molecules downstream of the APC gene product can be considered as targets for pharmacological intervention. Traf2 and Nck‐interacting protein kinase (TNIK) was identified as a regulatory component of the β‐catenin and T‐cell factor‐4 (TCF‐4) transcriptional complex. Several small‐molecule compounds targeting this protein kinase have been shown to have anti‐tumor effects against various cancers. An anthelmintic agent, mebendazole, was recently identified as a selective inhibitor of TNIK and is under clinical evaluation. TNIK regulates Wnt signaling in the most downstream part of the pathway, and its pharmacological inhibition seems to be a promising therapeutic approach. We demonstrated the feasibility of this approach by developing a small‐molecule TNIK inhibitor, NCB‐0846.

Trop2 and its overexpression in cancers: regulation and clinical/therapeutic implications

Trop2 is a transmembrane glycoprotein encoded by the Tacstd2 gene. It is an intracellular calcium signal transducer that is differentially expressed in many cancers. It signals cells for self-renewal, proliferation, invasion, and survival. It has stem cell-like qualities. Trop2 is expressed in many normal tissues, though in contrast, it is overexpressed in many cancers and the overexpression of Trop2 is of prognostic significance. Several ligands have been proposed that interact with Trop2. Trop2 signals the cells via different pathways and it is transcriptionally regulated by a complex network of several transcription factors. Trop2 expression in cancer cells has been correlated with drug resistance. Several strategies target Trop2 on cancer cells that include antibodies, antibody fusion proteins, chemical inhibitors, nanoparticles, etc. The in vitro studies and pre-clinical studies, using these various therapeutic treatments, have resulted in significant inhibition of tumor cell growth both in vitro and in vivo in mice. A clinical study is underway using IMMU-132 (hrS7 linked to SN38) in patients with epithelial cancers. This review describes briefly the various characteristics of cancer cells overexpressing Trop2 and the potential application of Trop2 as both a prognostic biomarker and as a therapeutic target to reverse resistance.

De novo assembly and characterization of Muscovy duck liver transcriptome and analysis of differentially regulated genes in response to heat stress

High temperature is a major abiotic stress limiting animal growth and productivity worldwide. The Muscovy duck (Cairina moschata), sometimes called the Barbary drake, is a type of duck with a fairly unusual domestication history. In Southeast Asia, duck meat is one of the top meats consumed, and as such, the production of the meat is an important topic of research. The transcriptomic and genomic data presently available are insufficient to understanding the molecular mechanism underlying the heat tolerance of Muscovy ducks. Thus, transcriptome and expression profiling data for this species are required as important resource for identifying genes and developing molecular marker. In this study, de novo transcriptome assembly and gene expression analysis using Illumina sequencing technology were performed. More than 225 million clean reads were generated and assembled into 36,903 unique transcripts with an average length of 1,135 bp. A total of 21,221 (57.50 %) unigenes were annotated. Gene Ontology (GO) analysis of the annotated unigenes revealed that the majority of sequenced genes were associated with transcription, signal transduction, and apoptosis. We also performed gene expression profiling analysis upon heat treatment in Muscovy ducks and identified 470 heat-response unique transcripts. GO term enrichment showed that protein folding and chaperone binding were significant enrichment, whereas KEGG pathway analyses showed that Ras and MAPKs were activated after heat stress in Muscovy ducks. Our research enriched sequences information of Muscovy duck, provided novel insights into responses to heat stress in these ducks, and serve as candidate genes or markers that can be used to guide future efforts to breed heat-tolerant duck strains.

The E3 ubiquitin ligase MID1 catalyzes ubiquitination and cleavage of Fu

SHH (Sonic Hedgehog)-GLI signaling plays an important role during embryogenesis and in tumorigenesis. The survival and growth of several types of cancer depend on autonomously activated SHH-GLI signaling. A protein complex containing the ubiquitin ligase MID1 and protein phosphatase 2A regulates the nuclear localization and transcriptional activity of GLI3, a transcriptional effector molecule of SHH, in cancer cell lines with autonomously activated SHH signaling. However, the exact molecular mechanisms that mediate the interaction between MID1 and GLI3 remained unknown. Here, we show that MID1 catalyzes the ubiquitination and proteasomal cleavage of the GLI3 regulator Fu. Our data suggest that Fu ubiquitination and cleavage is one of the key elements connecting the MID1-PP2A protein complex with GLI3 activity control.

Non-metastatic 2 (NME2)-mediated suppression of lung cancer metastasis involves transcriptional regulation of key cell adhesion factor vinculin

Tumor metastasis refers to spread of a tumor from site of its origin to distant organs and causes majority of cancer deaths. Although >30 metastasis suppressor genes (MSGs) that negatively regulate metastasis have been identified so far, two issues are poorly understood: first, which MSGs oppose metastasis in a tumor type, and second, which molecular function of MSG controls metastasis. Herein, integrative analyses of tumor-transcriptomes (n = 382), survival data (n = 530) and lymph node metastases (n = 100) in lung cancer patients identified non-metastatic 2 (NME2) as a key MSG from a pool of >30 metastasis suppressors. Subsequently, we generated a promoter-wide binding map for NME2 using chromatin immunoprecipitation with promoter microarrays (ChIP-chip), and transcriptome profiling. We discovered novel targets of NME2 which are involved in focal adhesion signaling. Importantly, we detected binding of NME2 in promoter of focal adhesion factor, vinculin. Reduced expression of NME2 led to enhanced transcription of vinculin. In comparison, NME1, a close homolog of NME2, did not bind to vinculin promoter nor regulate its expression. In line, enhanced metastasis of NME2-depleted lung cancer cells was found in zebrafish and nude mice tumor models. The metastatic potential of NME2-depleted cells was remarkably diminished upon selective RNA-i-mediated silencing of vinculin. Together, we demonstrate that reduced NME2 levels lead to transcriptional de-repression of vinculin and regulate lung cancer metastasis.

Ciliopathies: the trafficking connection

The primary cilium (PC) is a very dynamic hair-like membrane structure that assembles/disassembles in a cell-cycle-dependent manner and is present in almost every cell type. Despite being continuous with the plasma membrane, a diffusion barrier located at the ciliary base confers the PC properties of a separate organelle with very specific characteristics and membrane composition. Therefore, vesicle trafficking is the major process by which components are acquired for cilium formation and maintenance. In fact, a system of specific sorting signals controls the right of cargo admission into the cilia. Disruption to the ciliary structure or its function leads to multiorgan diseases known as ciliopathies. These illnesses arise from a spectrum of mutations in any of the more than 50 loci linked to these conditions. Therefore, it is not surprising that symptom variability (specific manifestations and severity) among and within ciliopathies appears to be an emerging characteristic. Nevertheless, one can speculate that mutations occurring in genes whose products contribute to the overall vesicle trafficking to the PC (i.e. affecting cilia assembly) will lead to more severe symptoms, whereas those involved in the transport of specific cargoes will result in milder phenotypes. In this review, we summarize the trafficking mechanisms to the cilia and also provide a description of the trafficking defects observed in some ciliopathies which can be correlated to the severity of the pathology.

Interaction with the Bardet-Biedl gene product TRIM32/BBS11 modifies the half-life and localization of Glis2/NPHP7

Although the two ciliopathies Bardet-Biedl syndrome and nephronophthisis share multiple clinical manifestations, the molecular basis for this overlap remains largely unknown. Both BBS11 and NPHP7 are unusual members of their respective gene families. Although BBS11/TRIM32 represents a RING finger E3 ubiquitin ligase also involved in hereditary forms of muscular dystrophy, NPHP7/Glis2 is a Gli-like transcriptional repressor that localizes to the nucleus, deviating from the ciliary localization of most other ciliopathy-associated gene products. We found that BBS11/TRIM32 and NPHP7/Glis2 can physically interact with each other, suggesting that both proteins form a functionally relevant protein complex in vivo. This hypothesis was further supported by the genetic interaction and synergist cyst formation in the zebrafish pronephros model. However, contrary to our expectation, the E3 ubiquitin ligase BBS11/TRIM32 was not responsible for the short half-life of NPHP7/Glis2 but instead promoted the accumulation of mixed Lys(48)/Lys(63)-polyubiquitylated NPHP7/Glis2 species. This modification not only prolonged the half-life of NPHP7/Glis2, but also altered the subnuclear localization and the transcriptional activity of NPHP7/Glis2. Thus, physical and functional interactions between NPHP and Bardet-Biedl syndrome gene products, demonstrated for Glis2 and TRIM32, may help to explain the phenotypic similarities between these two syndromes.

An integrative view on the physiology of human early placental villi

The placenta is an indispensable organ for intrauterine protection, development and growth of the embryo and fetus. It provides tight contact between mother and conceptus, enabling the exchange of gas, nutrients and waste products. The human placenta is discoidal in shape, and bears a hemo-monochorial interface as well as villous materno-fetal interdigitations. Since Peter Medawar's astonishment to the paradoxical nature of the mother-fetus relationship in 1953, substantial knowledge in the domain of placental physiology has been gathered. In the present essay, an attempt has been made to build an integrated understanding of morphological dynamics, cell biology, and functional aspects of genomic and proteomic expression of human early placental villous trophoblast cells followed by a commentary on the future directions of research in this field.

A complex of BBS1 and NPHP7 is required for cilia motility in zebrafish

Bardet-Biedl syndrome (BBS) and nephronophthisis (NPH) are hereditary autosomal recessive disorders, encoded by two families of diverse genes. BBS and NPH display several overlapping phenotypes including cystic kidney disease, retinitis pigmentosa, liver fibrosis, situs inversus and cerebellar defects. Since most of the BBS and NPH proteins localize to cilia and/or their appendages, BBS and NPH are considered ciliopathies. In this study, we characterized the function of the transcription factor Nphp7 in zebrafish, and addressed the molecular connection between BBS and NPH. The knockdown of zebrafish bbs1 and nphp7.2 caused similar phenotypic changes including convergent extension defects, curvature of the body axis, hydrocephalus, abnormal heart looping and cystic pronephros, all consistent with an altered ciliary function. Immunoprecipitation assays revealed a physical interaction between BBS1 and NPHP7, and the simultaneous knockdown of zbbs1 and znphp7.2 enhanced the cystic pronephros phenotype synergistically, suggesting a genetic interaction between zbbs1 and znphp7.2 in vivo. Deletion of zBbs1 or zNphp7.2 did not compromise cilia formation, but disrupted cilia motility. Although NPHP7 has been shown to act as transcriptional repressor, our studies suggest a crosstalk between BBS1 and NPHP7 in regulating normal function of the cilium.

An Inv(16)(p13.3q24.3)-encoded CBFA2T3-GLIS2 fusion protein defines an aggressive subtype of pediatric acute megakaryoblastic leukemia

To define the mutation spectrum in non-Down syndrome acute megakaryoblastic leukemia (non-DS-AMKL), we performed transcriptome sequencing on diagnostic blasts from 14 pediatric patients and validated our findings in a recurrency/validation cohort consisting of 34 pediatric and 28 adult AMKL samples. Our analysis identified a cryptic chromosome 16 inversion (inv(16)(p13.3q24.3)) in 27% of pediatric cases, which encodes a CBFA2T3-GLIS2 fusion protein. Expression of CBFA2T3-GLIS2 in Drosophila and murine hematopoietic cells induced bone morphogenic protein (BMP) signaling and resulted in a marked increase in the self-renewal capacity of hematopoietic progenitors. These data suggest that expression of CBFA2T3-GLIS2 directly contributes to leukemogenesis.

Context-dependent regulation of Wnt signaling through the primary cilium

The primary cilium is a highly conserved environmental sensor and modulator of fluid movement in tubular structures. The growing recognition of mutations among its many components has led to the discovery of new disorders collectively called ciliopathies. Ciliary dysfunction disturbs a variety of signaling pathways along its basal body and axoneme that are critical for embryonic development and cell and organ homeostasis. Among the many pathways, here we discuss the emerging role of Wnt proteins in morphogenic signaling and ciliary biology during health and disease.

The ciliary protein nephrocystin-4 translocates the canonical Wnt regulator Jade-1 to the nucleus to negatively regulate β-catenin signaling

Nephronophthisis (NPH) is an autosomal-recessive cystic kidney disease and represents the most common genetic cause for end-stage renal disease in children and adolescents. It can be caused by the mutation of genes encoding for the nephrocystin proteins (NPHPs). All NPHPs localize to primary cilia, classifying this disease as a "ciliopathy." The primary cilium is a critical regulator of several cell signaling pathways. Cystogenesis in the kidney is thought to involve overactivation of canonical Wnt signaling, which is negatively regulated by the primary cilium and several NPH proteins, although the mechanism remains unclear. Jade-1 has recently been identified as a novel ubiquitin ligase targeting the canonical Wnt downstream effector β-catenin for proteasomal degradation. Here, we identify Jade-1 as a novel component of the NPHP protein complex. Jade-1 colocalizes with NPHP1 at the transition zone of primary cilia and interacts with NPHP4. Furthermore, NPHP4 stabilizes protein levels of Jade-1 and promotes the translocation of Jade-1 to the nucleus. Finally, NPHP4 and Jade-1 additively inhibit canonical Wnt signaling, and this genetic interaction is conserved in zebrafish. The stabilization and nuclear translocation of Jade-1 by NPHP4 enhances the ability of Jade-1 to negatively regulate canonical Wnt signaling. Loss of this repressor function in nephronophthisis might be an important factor promoting Wnt activation and contributing to cyst formation.

Gli-similar proteins: their mechanisms of action, physiological functions, and roles in disease

Gli-similar (Glis) 1-3 proteins constitute a subfamily of Krüppel-like zinc-finger proteins that are closely related to members of the Gli family. Glis proteins have been implicated in several pathologies, including cystic kidney disease, diabetes, hypothyroidism, fibrosis, osteoporosis, psoriasis, and cancer. In humans, a mutation in the Glis2 gene has been linked to the development of nephronophthisis (NPHP), a recessive cystic kidney disease, while mutations in Glis3 lead to an extended multisystem phenotype that includes the development of neonatal diabetes, polycystic kidneys, congenital hypothyroidism, and facial dysmorphism. Glis3 has also been identified as a risk locus for type-1 and type-2 diabetes and additional studies have revealed a role for Glis3 in pancreatic endocrine development, β-cell maintenance, and insulin regulation. Similar to Gli1-3, Glis2 and 3 have been reported to localize to the primary cilium. These studies appear to suggest that Glis proteins are part of a primary cilium-associated signaling pathway(s). It has been hypothesized that Glis proteins are activated through posttranslational modifications and subsequently translocate to the nucleus where they regulate transcription by interacting with Glis-binding sites in the promoter regions of target genes. This chapter summarizes the current state of knowledge regarding mechanisms of action of the Glis family of proteins, their physiological functions, as well as their roles in disease.

Identification of nuclear localization, DNA binding, and transactivating mechanisms of Kruppel-like zinc finger protein Gli-similar 2 (Glis2)

Gli-similar 1-3 (Glis1-3) constitute a subfamily of Krüppel-like zinc finger (ZF) transcription factors that are closely related to the Gli protein family. Mutations in GLIS2 are linked to nephronophthisis, a chronic kidney disease characterized by renal fibrosis and atrophy in children and young adults. Currently, very little information exists about the mechanism of action of Glis2, its target genes, or the signaling pathways that regulate its activity. In this study, we show that a region within ZF3 is required for the nuclear localization of Glis2. Analysis of Glis2 DNA binding demonstrated that Glis2 binds effectively to the consensus Glis binding sequence (GlisBS) (G/C)TGGGGGGT(A/C). Although Glis2 was unable to induce transactivation of a GlisBS-dependent reporter, it effectively inhibited the GlisBS-mediated transactivation by Gli1. Mutations that disrupt the tetrahedral configuration of each ZF within Glis2 abolished Glis2 binding to GlisBS and also abrogated its inhibition of Gli1-mediated transactivation. In contrast, Glis2 was able to activate the murine insulin-2 (Ins2) promoter by binding directly to two GlisBS elements located at -263 and -99 within the Ins2 promoter. Phosphomimetic mutation of Ser(245) inhibited the binding of Glis2 to GlisBS and dramatically affected its transactivation of the Ins2 promoter and its ability to inhibit GlisBS-dependent transactivation by Gli1. In this study, we demonstrate that Glis2 can function as a transcriptional activator and that post-translational modification within its DNA-binding domain can regulate its transcriptional activity. This control may play a critical role in the Glis2-dependent regulation of target genes and renal function.

Gli-similar (Glis) Krüppel-like zinc finger proteins: insights into their physiological functions and critical roles in neonatal diabetes and cystic renal disease

GLI-similar (Glis) 1-3 proteins constitute a subfamily of the Krüppel-like zinc finger transcription factors that are closely related to the Gli family. Glis1-3 play critical roles in the regulation of a number of physiological processes and have been implicated in several pathologies. Mutations in GLIS2 have been linked to nephronophthisis, an autosomal recessive cystic kidney disease. Loss of Glis2 function leads to renal atrophy and fibrosis that involves epithelial-mesenchymal transition (EMT) of renal tubule epithelial cells. Mutations in human GLIS3 have been implicated in a syndrome characterized by neonatal diabetes and congenital hypothyroidism (NDH) and in some patients accompanied by polycystic kidney disease, glaucoma, and liver fibrosis. In addition, the GLIS3 gene has been identified as a susceptibility locus for the risk of type 1 and 2 diabetes. Glis3 plays a key role in pancreatic development, particularly in the generation of ß-cells and in the regulation of insulin gene expression. Glis2 and Glis3 proteins have been demonstrated to localize to the primary cilium, a signaling organelle that has been implicated in several pathologies, including cystic renal diseases. This association suggests that Glis2/3 are part of primary cilium-associated signaling pathways that control the activity of Glis proteins. Upon activation in the primary cilium, Glis proteins may translocate to the nucleus where they subsequently regulate gene transcription by interacting with Glis-binding sites in the promoter regulatory region of target genes. In this review, we discuss the current knowledge of the Glis signaling pathways, their physiological functions, and their involvement in several human pathologies.

Tiermodelle mit Zystennieren

Polyzystische Nierenerkrankungen (PKD) sind der häufigste genetische Grund für ein terminales Nierenversagen. Flüssigkeitsgefüllte Zysten bilden sich im Nierenparenchym und beeinträchtigen die Nierenfunktion mit zunehmender Anzahl und Größe, bis diese vollkommen zum Erliegen kommt. Seit mehreren Jahrzehnten werden Tiermodelle mit PKD für die Aufklärung der molekularen Mechanismen der Zystogenese verwendet. War man anfangs auf zufällige, durch Spontanmutationen aufgetretene Zystenmodelle angewiesen, eröffneten transgene und Knock-out-Technologien in den letzen 20 Jahren eine völlig neue Dimension, die molekularen Pathomechanismen der Zystogenese durch gezielte genetische Veränderungen im Erbgut aufzuklären. Nur mit der Hilfe von Tiermodellen konnte die Lokalisation von „Zystenproteinen“ in den Zilien und die Beteiligung zilienabhängiger Signalkaskaden in der Zystogenese gezeigt werden. Dieser Artikel gibt einen Überblick über die derzeit vorhandenen murinen Tiermodelle mit PKD.

Cystic kidney disease: the role of Wnt signaling

Wnt signaling encompasses a variety of signaling cascades that can be activated by secreted Wnt ligands. Two such pathways, the canonical or beta-catenin pathway and the planar cell polarity (PCP) pathway, have recently received attention for their roles in multiple cellular processes within the kidney. Both of these pathways are important for kidney development as well as homeostasis and injury repair. The disruption of either pathway can lead to cystic kidney disease, a class of genetic diseases that includes the most common hereditary life-threatening syndrome polycystic kidney disease (PKD). Recent evidence implicates canonical and noncanonical Wnt pathways in cyst formation and points to a remarkable role for developmental processes in the adult kidney.

Impaired Wnt-beta-catenin signaling disrupts adult renal homeostasis and leads to cystic kidney ciliopathy

Cystic kidney disease represents a major cause of end-stage renal disease, yet the molecular mechanisms of pathogenesis remain largely unclear. Recent emphasis has been placed on a potential role for canonical Wnt signaling, but investigation of this pathway in adult renal homeostasis is lacking. Here we provide evidence of a previously unidentified canonical Wnt activity in adult mammalian kidney homeostasis, the loss of which leads to cystic kidney disease. Loss of the Jouberin (Jbn) protein in mouse leads to the cystic kidney disease nephronophthisis, owing to an unexpected decrease in endogenous Wnt activity. Jbn interacts with and facilitates beta-catenin nuclear accumulation, resulting in positive modulation of downstream transcription. Finally, we show that Jbn is required in vivo for a Wnt response to injury and renal tubule repair, the absence of which triggers cystogenesis.

Pygopus and the Wnt signaling pathway: a diverse set of connections

Identification of Pygopus in Drosophila as a dedicated component of the Wg (fly homolog of mammalian Wnt) signaling cascade initiated many inquiries into the mechanism of its function. Surprisingly, the nearly exclusive role for Pygopus in Wg signal transduction in flies is not seen in mice, where Pygopus appears to have both Wnt-related and Wnt-independent functions. This review addresses the initial findings of Pygopus as a Wg/Wnt co-activator in light of recent data from both fly and mammalian studies. We compare and contrast the developmental phenotypes of pygopus mutants to those characterized for known Wg/Wnt transducers and explore the data regarding a role for mammalian Pygopus 2 in tumorigenesis. We further analyze the roles of the two conserved domains of Pygopus proteins in transcription, and propose a model for the molecular mechanism of Pygopus function in both Wg/Wnt signaling and Wnt-independent transcriptional regulation.

Wnt signaling inside the nucleus

Accumulation of the beta-catenin protein and transactivation of a certain set of T-cell factor (TCF)-4 target genes by accumulated beta-catenin have been considered crucial in colorectal carcinogenesis. In the present review, we summarize nuclear proteins that interact with, and regulate, the beta-catenin and TCF and lymphoid enhancer factor (LEF) transcriptional complexes. Our recent series of proteomic studies has also revealed that various classes of nuclear proteins participate in the beta-catenin-TCF-4 complex and modulate its transcriptional activity. Furthermore, the protein composition of the TCF-4-containing nuclear complex is not fixed, but is regulated dynamically by endogenous programs associated with intestinal epithelial cell differentiation and exogenous stimuli. Restoration of the loss-of-function mutation of the adenomatous polyposis coli (APC) gene in colorectal cancer cells does not seem to be a realistic approach with currently available medical technologies, and only signaling molecules downstream of the APC gene product can be considered as targets of pharmacological intervention. Nuclear proteins associated with the beta-catenin-TCF-4 complex may include feasible targets for molecular therapy against colorectal cancer. Recently, an inhibitor of the interaction between CREB-binding protein and beta-catenin was shown to efficiently shut down the transcriptional activity of TCF-4 and induce apoptosis of colorectal cancer cells. We also summarize current strategies in the development of drugs against Wnt signaling.

Kruppel-like zinc finger protein Glis2 is essential for the maintenance of normal renal functions

To obtain insight into the physiological functions of the Krüppel-like zinc finger protein Gli-similar 2 (Glis2), mice deficient in Glis2 expression were generated. Glis2 mutant (Glis2(mut)) mice exhibit significantly shorter life spans than do littermate wild-type (WT) mice due to the development of progressive chronic kidney disease with features resembling nephronophthisis. Glis2(mut) mice develop severe renal atrophy involving increased cell death and basement membrane thickening in the proximal convoluted tubules. This development is accompanied by infiltration of lymphocytic inflammatory cells and interstitial/glomerular fibrosis. The severity of the fibrosis, inflammatory infiltrates, and glomerular and tubular changes progresses with age. Blood urea nitrogen and creatinine increase, and Glis2(mut) mice develop proteinuria and ultimately die prematurely of renal failure. A comparison of the gene expression profiles of kidneys from 25-day-old/60-day-old WT and Glis2(mut) mice by microarray analysis showed increased expressions of many genes involved in immune responses/inflammation and fibrosis/tissue remodeling in kidneys of Glis2(mut) mice, including several cytokines and adhesion and extracellular matrix proteins. Our data demonstrate that a deficiency in Glis2 expression leads to tubular atrophy and progressive fibrosis, similar to nephronophthisis, that ultimately results in renal failure. Our study indicates that Glis2 plays a critical role in the maintenance of normal kidney architecture and functions.